1. Field of the Invention
The present invention relates generally to a display system for understanding the status of a complex process and its components, and more particularly, to a system that presents a large quantity of information in a manner that is readily absorbed and easily understood.
2. Background Information
Fault management, the identification of and response to abnormal conditions, is a major component of a humans role in many complex tactical environments such as process control, flight decks and air traffic control. Operational history, design reviews and evaluation studies have shown a large number of major deficiencies with traditional systems, particularly with respect to the operator's role. The deficiencies are rarely due to a lack of alarm data; rather, they are the result of problems in finding and integrating the relevant data out of a much larger set.
The significance of data problem represents an inability to find, integrate, or interpret the "right" data at the "right" time (e.g., critical information is not detected among the ambient data load, or not assembled from data distributed over a time or space, when not looked for due to misunderstandings or erroneous assumptions). This problem occurs in situations where a large amount of potentially relevant data must be sifted to find the significant subset for the current context. In other words, most information handling problems are not due to a lack of data but rather due to an overabundance of unorganized data.
Operational staff members in dynamic process environments must detect, evaluate and respond to abnormal conditions. Traditionally, operators must sift through large numbers of what are traditionally called "alarm" messages to find and identify the abnormal conditions that are indicated by "alarms". Conventional data display systems complicate the operator's task by producing alarm signals which are triggered when signals cross threshold crossing type events which provide weak evidence with respect to underlying abnormal conditions. The alarms are organized according to system thereby requiring the operator to understand the relationships between components in various systems and the multiple functions they perform to determine whether the triggering events indicate an abnormality and where that abnormality might be occurring. Conventional display systems presentation methods range from completely parallel to totally serial. The parallel presentation systems complicate the operator's task because of the amount of information presented can overwhelm the operator, even though there are advantages in presenting all information at once. On the other hand, the serial presentation systems limit the number of messages, yet complicate the operator's integration problem because the operator must scan a long list of information one display page at a time to ferret out the relevant ones. The task of the operators in interpreting the evidence provided by these weak "alarms" is difficult because (a) the meaning of a particular alarm message depends on context, for example, plant mode, message history and the status of other messages and (b) the individual alarm messages must be selected and integrated to access process status since each message is only a partial and indirect indicator of an abnormality. Operator performance literature is full of cases where operators failed to correctly find, integrate, and interpret typical alarm messages in order to identify and respond to disturbances.
Failure to recognize the above-discussed problems has lead to the development of a number of computerized display systems which in many cases fail to improve the situation and in some instances can even exacerbate the system deficiencies because of a proliferation of types and degrees of displays. U.S. Pat. No. 4,816,208 issued Mar. 28, 1989, and assigned to the assignee of this application, describes a number of these prior art display systems.
The conventional approach for alarm systems used in nuclear power plants is to employ devices such as level sensors, flow sensors and valve position sensors to monitor the power plant. The outputs produced by these indicators are evaluated by signal monitoring units which include threshold or set point detectors. Each detector monitors a single sensor and produces an alarm signal that provides weak evidence of an abnormality. For example, an alarm in this type of system might signal that a valve is closed. Under one set of plant conditions, this valve position may be abnormal, i.e., no flow even when the system of which the valve is a part should be on. Under other conditions, it may not indicate an abnormality. The sensor signals are generally organized along system lines that reflect how components are arranged and are presented on the display grouped according to such systems. The display typically consists of backlit annunciator tiles each having a fixed wording message, and presents all of the "alarms" in parallel according to the system groupings. Each time a monitored piece of equipment crosses a threshold, a tile is turned on or off indicating that the threshold was crossed. In such a system, there is a problem in integrating these kinds of alarms into an overall understanding of plant state. The parallel presentation via the tiles theoretically allows the operator to get a "picture" of the operation of the entire system, yet it can overwhelm the operator when a major system disturbance occurs.
The aforereferenced U.S. Pat. No. 4,816,208, goes on to describe a number of other prior art systems that have tried to deal with the manner of organizing and presenting data to the operator of a complex process in a manner that can be readily absorbed and easily understood. The cited patent uses an intelligent rule based process to produce abnormality indicators which provide strong evidence of the problem. The abnormality indicators are organized according to function of the process and the alarms are sorted relating to violations of the goals of the function disturbances the process currently accomplishing the goals is experiencing and unavailability of the processes which could be used to achieve the goal. The messages are presented on a parallel display divided according to function and within each function by goal violation, process disturbance and process unavailability. The arrangement significantly simplified the presentation to the operator, however it still left room for improvement.
Accordingly, it is an object of this invention to further improve the organization and presentation of information within a display of a complex process to focus the operator on the information needed for any action required in an efficient manner.